Method for centrifugal castings



May 12, 1964 E. R. BIBBY 3,132,337.

METHOD FOR CENTRIFUGAL CASTINGS Filed Feb. 8, 1960 2 Sheets-Sheet 1 FIG. 3

INVENTOI? EDWARD R. 8/88) ATTORNEYS May 12, 1964 E. R. BIBBY 3,132,387

METHOD FOR CENTRIFUGAL CASTINGS Filed Feb. 8. 1960 2 Sheets-Sheet 2 j FIG. 6 FIG. 5

m/mvroe 1 EDWARD 8. may

eraz wfi' ATTORNEYS United States Patent 3,132,387 METHOD FOR CENTRIFUGAL CASTINGS Edward R. Bibby, Bibby'Foundry Ltd, Box 279, Galt, Ontario, Canada Filed Feb. 8, 1960, Ser. No. 7,446 3 Claims. (Cl. 22-192) This invention relates to the casting of tubular articles such as soil pipe.

' More particularly, it relates to a method for centrifugal ly casting such articles.

The casting of tubular articles by centrifugal methods is not broadly new. There are at least two generally accepted methods. There is the green sand spun method in which a conventional damp moulding sand is rammed, slung, blown or packed into a moulding tube or box following which the metal is poured and the casting spun. This method requires large quantities of sand and costly sand handling equipment.

There is also the so called permanent mould method of casting in which no sand is used. The article is spun in a mould which although termed as permanent must be replaced at periodic intervals.

it is an object of this invention to centrifugally cast tubular articles by a method that avoids the large quantitles of sand and the costly sand handling equipment of the green sand spun method and that avoids the costly replacement of the so called permanent mould of the permanent mould method.

According to this invention a quantity of a loose compactable settable moulding composition having therein a binder that is settable by the application thereto of a setting gas is coated evenly over the inside wall of a moulding tube and a setting gas is forced thercagainst to harden the coating. A quantity of moulding material is then poured into the moulding tube and centrifugally cast into a tubular shape against the set moulding composition according to standard centrifugal moulding practice. Following the centrifugal casting in the usual way, the cast article is removed from the tube and the process is repeated.

The moulding composition can comprise a mixture of silica sand bound by an alkaline silicate, such as sodium silicate, which is settable by gaseous carbon dioxide. The carbon dioxide process for setting moulding compositions having an alkaline silicate binder is generally well-known in static applications, and a good general discussion thereof is to be found in a technical paper entitled The Carbon Dioxide Process by D. V. Atterton, published in a publication entitled 'Foundry Trade Journal on May 12, 1955. The said publication is of record in the Scientific Library of the Patent Office of the United States of America.

:In the drawings,

FIGURE 1 is a perspective view of apparatus for practicing this invention.

FIGURE 2 is an end view along the line 22 illustrating the means tor mounting the free end of the trough spreader assembly.

FIGURE 3 is a view along the line 3-3 showing the mannerin which the trough spreader assembly is mounted at the retained end. 7

FIGURE 4 is a cross-sectional View of the moulding tube illustrating the trough spreader assembly as it is inserted initially into the moulding tube.

FIGURE 5 is an end view of the trough spreader assembly operating lever atter the trough has been dumped.

FIGURE 6 is a cross-sectional View similar to FIG- URE 4 showing the trough spreader assembly in the dumped position of FIGURE 5.

FIGURE 7 is an end view of the operating mechanism for the trough spreader assembly in which the spreader is in an operative position.

EIGURE 8 is a cross-sectional view of the moulding tube illustrating the spreader in the operative position.

FIGURE 9 is a view of a horn for pouring molten metal into the moulding tube.

Referring to the drawings the numeral 10 generally indicates apparatus for practicing the method of this in vention. It comprises a base 12 having means thereon for mounting a moulding tube in a horizontal position and means for depositing a moulding composition in the tube and for spreading it evenly on the inside wall thereof.

The moulding tube 14 is made of steel and has tor-aminous side walls and open ends. It is cradled between rotatably mounted discs 16 that are power rotated by a drive means (not shown) common in the centrifugal casting art. It will be noted that the moulding tube 14 has shoulders inwardly of each of its ends which serve to limit the movement of the tube longitudinally of itself as it is rotated in use under the action of the discs 16.

A bracket 13 pivotally mounted on the base as at 20 has idling rollers 22 that rest on the top of the tube 14 under the influence of the counter-balancing weight 24. Bracket 18 maintains the required amount of pressure against the tube to keep it on the discs 16 as the discs are rotated in use. It can be removed by manual rotation against the force of weight 24.

As indicated above a moulding composition, such as clean silica sand moistened with sodium silicate, that is compactable initially and which can be set by the application thereto of a setting gas is deposited on the inside wall of the horizontally disposed moulding tube 14 substantially along the full extent thereof. Subsequent to this the moulding composition is evenly coated to the inside wall of the moulding tube 14 by means of an elongated spreader as the spreader and tube rotate relatively to each other. These things are done in the embodiment of the invention herein described by means of the trough 26, an elongated spreader blade 28 and the cooperating parts carried by the carriages 30 and 32.

Carriage 30 is slidable longitudinally of the base 12 on opposed tracks 34. Carriage 32 is slidable longitudinally of the base 12 on opposed tracks 36.

Carriage 30 has a bracket 38 rigidly mounted thereon to which the inner race of a bearing cap 40 is rigidly connected by means of the arm 42. Bearing cap 40 is adapted to enter into the open end of the mouldingtube 14 and it comprises an inner race of a ball-bearing assembly that is rigidly mounted as indicated above and an outer race that is free to turn with respect to the inner race. Theouter circumference of the outer race enters into the open end of the moulding tube and is adapted to be fixed with respect thereto by means of bolts 41 that pass through the moulding tube and are tightened against the outer race.

The trough 26 and the spreader 28 are carried by a rod 44 which is in turn carried by and journalled in the carriage 46. Carriage 46 is free to slide transversely of the longitudinal axis of the moulding tube 14 within the key-way 48. It will be noted that the inner race of the bearing cap 49' that is rigidly connected to the bracket 38 by arm 42 is provided with an elongated slot 50 (FIG- URE 3) to permit this transverse movement of the rod. The bracket 38 is also formed with a slot similar to the slot 50 for the same purpose.

A tube 52 formed with a series of holes along its length and closed at its free end is rigidly mounted on the rod 44 and connects at its other end with a gas supply tube 54.

As will be explained later, the trough spreader assembly on the rod 44 is extended into the tube 14 as the carriage 30 is moved towards the right as viewed in FIGURE 1.

A bearing cap 56, similar to the bearing cap 40, is mounted on the bracket 58 of the carriage 32 which during the application of the moulding material engages in the end of the moulding tube 14. Bearing cap 56 is also of the ball-bearing type and the inner race thereof is rigidly mounted to the bracket 56. The outer race is rotatable with respect to the inner race and is secured to the moulding tube by means of manually tightenable screws 60. I

As the carriage 30 is moved to the right to carry the trough spreader assembly into the moulding tube 14 the free end of the rod 44 passes through an elongated slot 62 in the bearing cap 56 and becomes journalled in the opening 64 in the free end of the piston rod 66 of the piston 68. Piston 68 is pneumatically or hydraulically operated to move its piston rod 66 and therefore the rod 44 carried thereby in a direction transversely of the longitudinal axis of the base 12 as will be described later.

A piston 70 at the left hand side of the machine has a piston rod 72, the free end of which engages with the rod 44 to move it and the carriage 46 within which the rod is mounted in a direction transversely of the iongitudinal axis of the base 12, as will be described later.

Means are provided for inverting the trough 26 which comprise a lever 74 rigidly connected to the rod 44. By turning the lever 74 from the position illustrated in FIG- URE 1 to the position illustrated in FIGURE 5, the trough 26 is inverted and the contents thereof dumped. If the trough is evenly filled it will be apparent that the contents are spread evenly along the length of the horizontally disposed tube 14 in this manner because trough 26 is substantially coextensive with the moulding tube.

A pin 76 is provided for locking the trough in an upright or an inverted position with respect to the rod. It passes through aligned holes in the lever and in the piston rod 72 of piston 70.

A hopper 78 that can be raised or lowered in the direction of the arrow is provided for supplying moulding composition to the trough as it is projected into the moulding tube in use. A shut off valve 8% controls the flow. A waste chute 82 is provided to take the excess.

After the moulding composition has been applied to and set on the inside of the moulding tube 14, the bearings 56 and 40 are removed and moulding caps inserted into the open ends of the moulding tube prior to the pouring of the metal. The moulding cap 84 at the right hand end of the moulding tube as view in FIGURE 1 has a central opening through which moulding metal from the pouring horn 86 can enter the tube. Pouring horn 86 is slidably mounted on a bar 88 and can be slid into position as required for the pouring operation.

In the embodiment of the invention shown it is contemplated that the moulding be cast in the same machinery as the sand is applied with. However, it will be apparent that it may be desirable in many cases to remove the moulding tube 14 from the apparatus illustrated in FIGURE 1 and send it to a different piece of apparatus for the actual casting of the tubular pipe.

Following is a procedure for applying a moulded composition to the inside of a tubular mould according to this invention.

One would fill the hopper 7 8 with a moulding composition that can be set, after it has been spread into position. I have found that a satisfactory composition can be made from a washed silica sand moistened with sodium silicate. Extensive technical information has been published on sodium silicate bonded sands. It is not intended in this specification to give details concerning their selection and use. It is only necessary that a compactable moulding composition having a binder that can be set by the application thereto of a setting gas be employed. By the term setting gas in this patent, I

mean a gas other than air. If sodium silicate bonded sands are employed, it is well-known that they can be set by the application thereto of gaseous carbon-dioxide. Many foundry sands will set with standing and drying. The sodium silicate bonded sand, however, has the advantage of setting quickly when treated with carbondioxide. Silica sand is also readily available and cheap. The moulding tube 14 is first set on the discs 16 and the idiers 22 of the retaining bracket 18 are permitted to rest on the top of the moulding tube as indicated in FIGURE 1.

Carriage 32 is then moved to the left so that the bearing cap 56 enters into the open end of the moulding tube and the screws 60 are tightened to rigidify the outer race of the bearing cap with respect to the moulding tube.

The carriage 30 is then moved from the position illustrated in FIGURE 1 with the cock of the sand hopper 78 open so that the trough 26 will fill with moulding composition as the trough spreader assembly is projected into the moulding tube. The hopper is raised and the flow of sand is shut oif as the left hand end of the hopper passes the hopper outlet. Projection of the trough assembly into the moulding tube 14 continues until the free end of the rod 44 is journalled within the opening 64 of the piston rod 66 of piston 68. At the same time screws 41 are tightened on the bearing cap 40.

The next step is to dump the sand from the trough 22 on the bottom of the horizontally disposed moulding tube 14. This is done by turning the lever 74 through 180 degrees and inserting the locking pin 76 as illustrated in FIGURES 5 and 6. The moulding composition 90 is thus dumped from the trough 26 and is evenly distributed along the bottom of the moulding tube 14.

The next step is to bring the longitudinally extending moulding edge of the spreader 28 into close proximity to the side wall of the moulding tube 14. This is done by operating the cylinders 68 and 70 to pull in their piston rods and carry the rod 44 with its attached scraper assembly rearwardly a predetermined amount to dispose the scraper as shown in FIGURE 8.

The moulding tube 14 is then rotated in the direction of the arrows of FIGURE 8 by turning the power operated rollers 16 to carry the moulding composition into contact with the blade whereby the blade co-operates with the side wall of the moulding tube 14- to spread the moulding composition evenly on the inside of the mould. Speed of rotation during the spreading operation will vary with the size of the tube. However, with a tube of 5 inch diameter, I have satisfactorily used speeds of about 500 r.p.rn.

The evenly spread moulding composition is set after the spreading operation by forcing carbon dioxide into the supply pipe 54 and through the tube 52 to impinge on the spread sand and set it as shown in FIGURE 8. The setting of a sodium silicate moulding composition by means of carbon dioxide is well-known in the art and the considerations relating thereto are not discussed in this application.

Once the coating of moulding composition is set the rotation of the moulding tube is stopped and the spreader assembly is returned to the position of FIGURE 6 by operation of lever 74 and withdrawn from the moulding tube. Bearing cap 56 is also loosened and withdrawn by movement of carriage 32 to the right.

If there is a slight excess of sand to that required for the coating it will be in the form of dry loose granules after the setting operation and can be blown from the tube with an air hose or otherwise removed.

Moulding caps such as the one 84 are then placed and secured in each open end of tube 14 and molten moulding material such as iron is poured through the opening of the cap 84 from a pouring horn such as the horn 86.

The moulding tube is rotated at a fast rate of speed to centrifugally cast a tubular form on the coating of mould ing composition. Centrifugal casting is wellknown in the art and it is not intended to discuss considerations relating thereto in this application. After casting and cooling the cast tube is removed from the moulding tube and the process is repeated.

A particular advantage of the herein described method of applying a moulding composition to the inside of a moulding tube is that the thickness of the moulding composition can be very much less than the thickness used in the conventional sand spun method. For example, with a moulding tube inches in diameter a coating of about A of an inch of moulding composition is practical. This will vary with the size of the moulding tube employed. This, in eifect, means that one can operate the process with very much less sand and can in fact make small tubular cross-sections that were diflicult if not impossible to make with the older sand spun method employing conventional moulding sands. Moreover, silica sand is in most localities very much cheaper than conventional moulding sands.

What I claim as my invention is:

l. A method of forming a liner within a foraminous tubular mould, against which liner molten metal can be centrifugally cast, comprising the steps of coating the inside wall of said foraminous tubular mould evenly with a coating of a settable moulding composition containing sand and sodium silicate, rotating said coating and said foraminous tubular mould about their longitudinal axis, and forcing CO gas into said coating by impinging said CO gas against the inner wall of said coating as said moulding tube and coating are rotated to cure said sodium silicate thereby setting said composition and forming said liner.

2. A method as claimed in claim 1 in which said moulding composition is coated on the inside wall of said foramino-us tubular mould as aforesaid by means of an elongated spreader having a longitudinal spreading surface substantially co-extensive with the length of said toraminous tubular mould maintained in close spaced relation to the inside wall of said foraminous tubular mould as said toraminous tubular mould is rotated and in which said CO gas is forced into said coating as aforesaid While the said spreader is maintained in contact with the coating.

3. A method as claimed in claim 1 in which said CO gas is forced against the inner wall of said coating composition =from substantially one end of said tubular mould to the other end thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,504,497 Perry Aug. 12, 1924 2,341,739 Olt Feb. 15, 1944 2,449,900 Johnson 'Sept. 21, 1948 2,731,690 Coupland et a1. Jan. 24-, 1956 2,856,655 Abbott Oct. 21, 1958 2,994,919 Schafer et al. Aug. 8, 1961 OTHER REFERENCES Foundry Trade Journal, Carbon-Dioxide Process (Atterton), May 12, 1955, pages 505-507. 

1. A METHOD OF FORMING A LINER WITHIN A FORAMINOUS TUBULAR MOULD, AGAINST WHICH LINER MOLTEN METAL CAN BE CENTRIFUGALLY CAST, COMPRISING THE STEPS OF COATING THE INSIDE WALL OF SAID FORAMINOUS TUBULAR MOULD EVENLY WITH A COATING OF A SETTABLE MOULDING COMPOSITION CONTAINING SAND AND SODIUM SILICATE, ROTATING SAID COATING AND SAID FORAMINOUS TUBULAR MOULD ABOUT THEIR LONGITUDINAL AXIS, AND FORCING A CO2 GAS INTO SAID COATING BY IMPINGING SAID CO2 GAS AGAINST THE INNER WALL OF SAID COATING AS SAID MOULDING TUBE AND COATING ARE ROTATED TO CURE SAID SODIUM SILICATE THEREBY SETTING SAID COMPOSITION AND FORMING SAID LINER. 